Dang i should've got on earlier .

The reason why tig is the best process for welding (when speed/production is not an issue) is that it leaves the smalleest heat affected zone, and when a weld fails this is where it will fail (thus the reason for proper pre and post heats in many materials). However because tig is such a slow and tedious process it will be a while till it replaces arc welding on pipelines, and also up here (canada that is ) to get your B pressure ticket to weld pressure vessels the can be no more than 1/8" of deformation when the weld is place in a heartbreaker a few different ways (i think thats the right measurement). All in all any process/welder will get the job done providing that it has the amperage capabilities to get proper pentration, and that the operator has the hand skills and knowledge to know whats happening, also remember that a cheap welder is a cheap welder .

With welded seam tubing, the best way to ensure maximum strenght and so that the weld seam won't pull apart is to place the seam on the inside of the bends as this ensures that it'll be under compression instead of tension, and when under compression steels have a much high yield strenght. And on that note a .25" welded seam tubing i think would be a more than sufficent replacement for .120 DOM tubing.

Also when selecting dom one had to be careful that the tube selected has a uniform thickness, as dom tubing has a tendacy to have differences due to the hot rolling process (ie flat stock ran through a set of tappered dies which fusion welds the stock together, or it can be extruded) that it undergoes.

 

UUUUUM yea, I'm pretty sure that building cages with the ARC is a bit before my time hence my comment about never hearing about it but knowing that the ARC is good for penitration its a no brainer (see The SnoMan)


Being 19 has its drawbacks

I'm learning as much as I can as fast as I can.

 

I wouldn't say arc welding was before your time, although its popularity has been becoming less and less over the years. I'm only 21 myself, but I grew up Arc welding, AC nonetheless. I've been welding for about 8 years now, and just recently purchased a new AC Arc welder which fits my fabrication needs quite well. For the thin stuff and Aluminum I weld it with my oxy-acetylene rig, now that is old school

As for pipe vs. DOM, I believe that I'm going to build the cage, sliders, bumpers etc on my next rig out of 1.5" sch 40 structural pipe. Around here it's only $56 a stick, compared to roughly $180 a stick for DOM. Plus a $89 bender is much more appealing than a $300+ one. I've been following the pipe vs. DOM debate on Pirate for some time now, and I personally would feel perfectly safe in a pipe cage for a trail rig. A comp. buggy I might go with DOM however, just for the higher strength to weight ratio that DOM has.<O</O

 

imo, For me the pipe vs. DOM is we do not drive in NASCAR hitting walls at 180 mph with the lightest designed rollcages. Plus, people were building roll cages with ARC welders for race cars before I was born.

-imo- If you are using pipe, I think (1/8 x 2) or DOM (.120x 1.75) is good enough.

re: 3/16 and 1/4 wall tubing

Usually min OD size of this wall tubing is 3". It weighes about 10 pounds per foot. At 50-60 feet used per cage that will be a pretty hefty cage.

To compare weights http://www.aedmotorsport.com

> The flux wire that ... recommends is crap and is notorious for having poor
> penetration. ...I'd never in a million years use it for building a cag

I agree. I bought a Hobart 135 (not exactly cheap) 120v welder and there is no way I would use it to weld a trailer that had anything more then a 1/8" frame. Never mind a roll cage. Generally speaking, on a fillet weld, for power you need 2x what the metal thickness is for the welder's rating. You just are not going to get the penetration needed using the flux core and 120v. I know, I tried. Makes great booger welds though.

Also, what is not told is when you use gas for the same machine it halves the metal thickness you can weld. The same machine using gas and solid wire (I use .023) you are lucky to get 1/8" welds done. Only good for sheet metal and exhaust work, imo.

If you are going to use flux wire, then I would go no smaller then a 210 amp 220v welder with solid wire and gas. What is not said about flux, is using a weave method is discouraged (read the packaging on the Lincoln welders and wire at Home Depot) and it is more for straight line welding without weaving.

 

Hey you got the same welder as we do , good info .

 

Man, this thread makes me naseous I can't believe snojob recomended mig with flux wire as your best bet of welding a cage. Oh wait, sure I can No question that tig is your best bet, but there is a reason that nearly all structural welding is done using arc. It makes me feel like an old fart hearing from folks who are more familiar with the mig than the arc rather than vice versa. Granted, when I build my cage I'll mig it, but I'll be using my Miller 210 with 25/75. My whole problem with migs is that a monkey can lay down a pretty weld with one, but the penetration will suck. I don't care how great the weld looks if it come apart on you. The arc welds on my truck aren't artwork, but I've never had one break. My best advice for using a mig is: Use gas, use a 220 machine rather than the little ones so many use, and practice your coupons. The coupons will give you a better idea if you have your machine set right to get the penetration you want before you actually fab whatever you are making.

 

I taught myself how to weld with an old Lincoln AC, I've gotten pretty good over the last year. Never was too good with the gas welding.

I've got that problem too

Pardon the ignorance but what are coupons, I gather they arn't what you find in the Sunday paper.

 

Coupons are small pieces of metal you use to practice welding on. I like to use short segments of 3/8"x3" plate, or with short sections of pipe for that type of welding.

 

Thanks for the clearafication

 

first time i heard that i thought the same thing, what??????? but yeah, like said just practice metal.

 

I think they call them coupons because they can really save your *** later on. If you're unsure of the heat you need you can weld the coupons (of the same material/thickness as your project) and then cut them to check penetration. This way you know how to weld the important stuff.

 

Just going to throw my .02 cents in here. On using pipe one of the biggest things is when bending it make sure the welded section of the pipe is to the inside of the bend, if you put it to the outside it gets thin, or can seperate which is why most suggest not using it.
BTW DOM doesn't equal the best, consider NHRA rules it's the minimum, prefered is Chromemoly tubing (and contrary to one post they are not one and the same)

 

If you want to test your welds (using common sense for your safety) one thing I have found handy is a pipe bender. I figure if the weld holds under my 12 ton bender and the metal piece bends instead of breaking, then I have it right, and can proceed with the project. I found wacking a piece (coupon) with a 12 pound sledge a good indicator too.

> If you are going to use flux wire, then I would go no smaller then a 210

That was a typo, I meant to say if you are going to use a MIG, then ...

 

One thing that should be mentioned: a possible area for failure in a weld is at the craters (ie start and stop of the weld bead), a good habit to get into is to tac a piece of scrap of similar size to the material at the start and stop points to elimate this possibilty of failure, and when welding pipe or something where you bring a weld all the way around and stop in the same place you started, is to continue the weld past the crater.

 

Same thing can be accomplished by letting off the trigger (MIG) for second. Then squeeze trigger and fill the crater. Crater fill is very important!

On the subject of flux core...It does a fine job if you know what you are doing. Yes the box store, 110V welders suck more than an industrial shop vac, but any MIG rated 230V or 460V will provide great results with flux core. Most people who've tried flux core have only tried it on a 110V welder. Its a whole different ballgame when you use a welder that can push the amps require to use flux. Myself, I prefer a flux/CO2 gas combo. Biggest advantage is welding out of position. It just like welding with a stick, but you dont have to compensate for the rod being consumed. Also you have to drag a flux wire, not push or weave.

Now, on the subject of welding in general. If all you've ever welded is the tack welds to hold your sheet metal in place before you apply 3 gallons of bondo, you have no business putting together a roll cage. Same goes for using a 110V for anything more than heat duct. If your going to build things that can get people killed, leave it to the pros who weld for a living. I you still want to weld you own stuff. Great! Go learn how first by taking a welding course. The one thing I hate about any form of wire welding, is everyone thinks they are a master welder because of how "easy" it is to pull the trigger and put down a bead. Its a lot more complex than that. Also, we people who weld for a living give advice about how to weld something...don't argue. Listen and absorb.

Stryder

P.S. If I have time tomorrow, I post the strengths of welded pipe vs. DOM